The present invention relates to the field of drill bits used in drilling through subterranean formation. More particularly, this invention is concerned with the arrangement of the cutter elements that are mounted on the face of the drill bit's face.
U.S. Pat. No. 5,265,685 to Keith, which is herein incorporated by reference for all that it contains, discloses a fixed cutting element drill bit provided with primary cutting elements which are spaced radially from each other across the face of the bit. During drilling, the gap between the cutting elements causes a ridge to be formed in the bottom of the well and the apex of the ridge is removed before reaching the face of the bit. In one form of the invention, the apex is broken off by utilization of the sides of the supports for the primary cutting elements.
U.S. Pat. No. 5,551,522 to Keith, which is herein incorporated by reference for all that it contains, discloses a fixed cutter drill bit including a cutting structure having radially-spaced sets of cutter elements. The cutter element sets preferably overlap in rotated profile and include at least one low profile cutter element and at least two high profile elements. The low profile element is mounted so as to have a relatively low exposure height. The high profile elements are mounted at exposure heights that are greater than the exposure height of the low profile element, and are radially spaced from the low profile element on the bit face. The high profile elements may be mounted at the same radial position but at differing exposure heights, or may be mounted at the same exposure heights but at different radial positions relative to the bit axis. Providing this arrangement of low and high profile cutter elements tends to increase the bit's ability to resist vibration and provides an aggressive cutting structure, even after significant wear has occurred.
U.S. Pat. No. 5,549,171 to Wilmot, which is herein incorporated by reference for all that it contains, discloses a fixed cutter drill bit including sets of cutter elements mounted on the bit face. Each set includes at least two cutters mounted on different blades at generally the same radial position with reset to the bit axis but having differing degrees of backrake. The cutter elements of a set may be mounted having their cutting faces out-of-profile, such that certain elements in the set are exposed to the formation material to a greater extent than other cutter elements in the same set. The cutter elements in a set may have cutting faces and profiles that are identical, or they may vary in size or shape or both. The bit exhibits increased stability and provides substantial improvement in ROP without requiring excessive WOB.
Examples of prior art drill bits are disclosed in U.S. Pat. No. 4,545,441 to Williamson, U.S. Pat. No. 4,981,184 to Knowlton, U.S. Pat. No. 6,164,394 to Wilmot, U.S. Pat. No. 4,932,484 to Warren, U.S. Pat. No. 5,582,261 to Keith, which are all herein incorporated by reference for all that they contain.